A252870 Number of n X 2 nonnegative integer arrays with upper left 0 and lower right n+2-4 and value increasing by 0 or 1 with every step right or down.

0, 1, 8, 26, 61, 120, 211, 343, 526, 771, 1090, 1496, 2003, 2626, 3381, 4285, 5356, 6613, 8076, 9766, 11705, 13916, 16423, 19251, 22426, 25975, 29926, 34308, 39151, 44486, 50345, 56761, 63768, 71401, 79696, 88690, 98421, 108928, 120251, 132431, 145510

Offset

1,3

Comments

Column 2 of A252876.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = (1/24)*n^4 + (5/12)*n^3 - (13/24)*n^2 - (11/12)*n + 1.

Empirical: G.f.: -x^2*(1+3*x-4*x^2+x^3) / (x-1)^5. - R. J. Mathar, Nov 21 2015

Example

All solutions for n=3:
..0..0....0..0....0..0....0..1....0..1....0..0....0..1....0..0
..0..0....0..0....0..1....1..1....0..1....0..1....0..1....1..1
..0..1....1..1....1..1....1..1....1..1....0..1....0..1....1..1

Crossrefs

Sequence in context: A002413 A218325 A363288 * A163121 A250352 A213039

Adjacent sequences: A252867 A252868 A252869 * A252871 A252872 A252873

Keyword

nonn

Author

R. H. Hardin, Dec 24 2014

Status

approved